One of the most common challenges in designing portable electronic devices is the generation and maintenance of a regulated voltage from an unregulated voltage source, such as a battery. Typically, a voltage regulator is used for this purpose. A voltage regulator may be designed a linear or switching device.
A linear regulator provides closed loop control to regulate the voltage at the load. This type of regulator may be used to provide a constant output voltage which has a lower magnitude than the unregulated voltage source.
A switching regulator, on the other hand, is a circuit that uses an energy-storage element, such as an inductor, to transfer energy from the unregulated power source to the load in discrete bursts. Feedback circuitry may be used to regulate the energy transfer to maintain a constant voltage at the load. Because the switching regulator operates to transfer energy in discrete bursts, it can be configured to step-up or step-down the voltage of the unregulated voltage source. Moreover, switching regulators are generally more efficient than linear regulators.
Various types of switching regulators are commonly used today in portable electronic devices. A buck converter is just one example. The buck converter is an inductor based regulator used to step-down or buck the unregulated voltage source. The boost converter, on the other hand, is an inductor based regulator used to step-up or boost the unregulated voltage source. In some applications, a buck-boost converter may be used to provide a regulated output that is higher, lower or the same as the unregulated voltage source. The buck-boost converter provides a regulated output over large variations in the unregulated voltage source, but tends to be less efficient than the buck or boost converter. Accordingly, it would be desirable to improve the efficiency of buck-boost converters.